This image shows just how curled up the embryo is at this stage. The head end of the embryo is on the left. The embryo now has 22 pairs of somites (building blocks of the musculoskeletal system) running along the back.

This is a crucial time for your developing baby as the neural tube, which will become the brain and spinal cord, is forming.

This week your baby begins to grow rapidly and will become much more recognizable as a baby over the next five weeks. There are three types of cell, each committed to a separate function. The first will form the skin and nervous system; the second forms blood vessels, muscles, and bones; the third forms the entire digestive system.

At this stage, it is the cells responsible for the spine and nervous system that are at work. Changing shape from a flat disc, the embryo starts to curl up. The edges of the groove that are already partially formed along the back gradually start to meet, closing and fusing to form a tube, which will become the brain and spinal cord. The last parts of the tube to close are at the very top of the head and finally at the base of the spine, two days later.

Taking care to get an adequate intake of folic acid in early pregnancy is essential to ensure that the neural tube closes completely, with no gaps.

You’re excited to be pregnant, but should you tell people yet?

Most parents-to-be wait to share their exciting news until after week 12 when the risk of miscarriage falls. You may, however, decide you want to confide in family and close friends. If they are people whom you would tell if you miscarried, then there is no harm in sharing your news.

Legally, you don’t have to tell your employer yet. The latest date you should inform your employer is 15 weeks before the beginning of the week in which your baby is due, but if you want time off for antenatal appointments before this, you’ll need to explain why.

Similarly, if your job involves anything that could be a health and safety risk (for example, heavy lifting or working with chemicals), you must inform your employer early so your role can be adapted. It’s also sensible to tell your boss the good news before office gossip about your expanding girth snowballs.

Your first reaction to finding out that your partner is pregnant might be to want to tell the world. After all, you may be excited or nervous and want to confide in people who you can trust. Think twice before telling lots of people and don’t do so without talking to your partner. Of course, your partner may find it hard to hide some aspects of pregnancy, such as nausea and vomiting.